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Daniels, J.M. 1982. A field survey of Microtus chrotorrhinus in St. Louis county, Minnesota, summer 1982. Final report submitted to the Minnesota Department of Natural Resources. 8 pp.


The objective of this study was to locate several areas whose habitat suggests the presence of rock voles (Microtus chrotorrhinus) in St. Louis County. Two of these sites were then trapped to determine whether populations of rock voles exist at these sites and to what extent. There have been no records of rock voles in St. Louis County since 1921.

The results show that M. chrotorrhinus was not present at either site, though trapping success was quite high (37% and 22% respectively). The animals that were captured represent species most often associated with rock voles. Similarity in habitat of the sites studied to those in Cook Co. where rock voles are found is noteworthy. There are several possible explanations for the absence of rock voles at these sites. 1) Local extinction due to habitat disturbance. 2) Though rock vole populations were high in Cook Co. during this same period, considerable climatic differences occur between these two areas due to the effect of Lake Superior. 3) Though several habitat components appear to be the same at both the Cook Co. and St. Louis Co. sites, the St. Louis County sites may be unsuitable for reasons not yet identified. 4) Differences in trapping methodology (use of live traps versus snap traps).

Further work in this area needs to be done to determine the extent of rock vole populations in NE Minnesota and throughout their range. The Ely area of northern St. Louis Co., is an area of increasing recreational use and protection and/or management of land for this species may be necessary. In addition, it may be desirable to attempt to re-introduce this species to (A) re-establish colonies in this area and (B) learn more about the extent to which specific habitat parameters and habitat disturbances influence the colonization of this species.

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